Fix a link mistake in CONTRIBUTING.md (#468)

The link of api-review-process.md in the doc should be updated.

Fix #443

CONTRIBUTING.md

@@ -31,7 +31,7 @@ Please do not:
   of time.
 * **DON'T** commit code that you didn't write. If you find code that you think is a good fit to add to .NET Core, file an issue and start a discussion before proceeding.
 * **DON'T** submit PRs that alter licensing related files or headers. If you believe there's a problem with them, file an issue and we'll be happy to discuss it.
-* **DON'T** add API additions without filing an issue and discussing with us first. See [API Review Process](docs/project-docs/api-review-process.md).
+* **DON'T** add API additions without filing an issue and discussing with us first. See [API Review Process](docs/project/api-review-process.md).
 
 ## Managed Code Compatibility